InSight has placed its thermal probe on the Martian surface. The next step is to push Jackhammer to a height of 5 meters and hope that it does not meet a big rock

The NASA InSight lander has finally placed its thermal probe on the surface of Mars. Heat flow and physical properties (HP³) was deployed on February 12, about one meter from SEIS, the Landers seismometer. Soon he will begin to make his way through the Martian soil.

If you start to get used to such feats, keep a few things in mind.

The lander is on Mars, a planet more than 50 million miles away and it takes about 6 months to get there. Once there, the landing gear had to perform a dangerous landing process to arrive intact at the surface. The landing site was chosen carefully and, for this stationary lander to do his job, he had to stick his landing.

Then comes the difficult part.

"In a few days we will finally give up the field using some of our instrument we call the mole."

Tilman Spohn, Senior Researcher HP3, German Aerospace Center.

Insight had to look carefully at its surroundings and decide where to place its instruments. After weeks of examination, he chose this specific spot for the HP³ Then comes the thermal probe, which is an engineering feat in itself.

"This thing weighs less than a pair of shoes, consumes less power than a Wi-Fi router and has to dig at least 10 feet [3 meters] on another planet, "said Hudson." It took us a lot of work to get a version capable of doing tens of thousands of hammer strokes without tearing themselves apart; some early versions failed before reaching 16 feet [5 meters]but the version we sent to Mars has proven its robustness time and time again. "

The purpose of this venture is to learn about the internal structure of Mars. The heat probe and the physical properties will measure the amount of heat coming out of the center of Mars. To do this, he must make his way through the planet.

"Our probe is designed to measure heat from inside Mars," said Sue Smrekar, assistant principal investigator at InSight, of NASA's Jet Propulsion Laboratory in Pasadena, California. "That's why we want to have it underground. Changes in surface temperature, due to the seasons and the day-night cycle, could add "noise" to our data. "

HP3 must reach at least 3 meters below the surface to do its job, but ideally, it would reach the mark of 5 meters, its maximum depth. The part of the probe that makes the penetration is called the mole, which measures 40 cm long. The mole will stop every 50 cm and measure the thermal conductivity of the soil. But you have to wait two days to cool down before measuring, because hammering will create friction that will warm the soil. This heat would introduce noise into the data.

Once the measurements are made, the thermal probe is then heated and further measurements are made to verify the thermal conductivity. Then the whole process is repeated. At this rate, it could take two weeks to reach the depth of 3 meters.

If the probe strikes a rock before 3 meters, the profile of the mission changes. If the depth is less than 3 meters, it will take a year to eliminate noise from thermal conductivity readings because the probe will not be sufficiently insulated from surface temperatures. This is the reason why so great care has been taken to choose a location for the probe.

"We chose the ideal landing site, with almost no rocks on the surface," said Troy Hudson, a researcher and JPL engineer, who helped design HP.³. "This gives us a reason to believe that there are not a lot of big rocks in the basement, but we have to wait and see what we will meet underground."

Other LGs have already dug into the surface of Mars, but the HP3 of InSight will surpass them all. The NASA Viking 1 Lander dug 22 cm (8.6 inches) deep. The Phoenix Lander, a cousin of InSight, has dug 18 cm deep.

"We are looking forward to breaking records on Mars," said HP³ Principal Investigator Tilman Spohn of the German Aerospace Center (DLR), who provided the thermal probe for the InSight mission.

But the first landers had a different mission: to sample the soil. In a sense, it's unfair to compare them. In addition, it is not surprising that our technology has evolved since these landers have had their day.

Understanding the heat of Mars is essential to understanding how it is formed, as well as other rocky planets, and how surface geology is formed. Mars retains the heat of its formation about 4 billion years ago and heat is also produced by radioactive decay in its interior.

"Most of the geology of the planet is the result of
heat, "said Smrekar." The volcanic eruptions of the ancient past were
driven by the flow of this heat, pushing and building the high mountains
Mars is famous for. "

The way heat travels through the Martian mantle and crust determines the characteristics of the surface. Mars is home to Olympus Mons, the highest volcano in the solar system. With nearly 25 km high, it is almost three times bigger than Mount. Everest. Mars is also home to Tharsus Montes, three shield-volcanoes with a height of 14 to 18 km. Just like the volcanoes on Earth, they were created when the magma was forced through cracks in the crust.

"We want to know what led the early volcanism and
climate change on Mars, "said Spohn. "How much heat started March
with? How much is left to drive his volcanism?

Scientists have modeled the interior of Mars based on the best available data. But the InSight HP3 and its SEIS instrument will answer many questions and clarify our understanding of the red planet.

"The planets are a bit like an engine, driven by the heat
that moves their internal parts around, "said Smrekar." With HP3,
we will lift the engine hood of Mars for the first time. "

But it's more than Mars. It's about understanding how all the rocky planets are formed. This includes Mars, Earth, rocky moons and all the other rocky planets in our solar system and others.

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